Kirito attempted dual wielding against Heathcliff, who was revealed to be Kayaba Akihiko, without using any Sword Skills, since Akihiko was the maker of the skill. However, Kirito accidentally unleashed the 27-hit Dual Blades Sword Skill «The Eclipse», which allowed Heathcliff to easily block every single hit and make use of the opening created by the post-motion delay.

According to Heathcliff, this skill is awarded to the player with the fastest reaction time and the chosen player is supposed to be the one who will stand against the final boss (Heathcliff) on the 100th Floor in the Ruby Palace, regardless of the outcome of the said battle.[6]

Kirito had discovered Dual Blades a year before the battle with The Gleam Eyes. However, as Kirito did not know the conditions of unlocking the skill, he chose to keep his skill a secret to avoid unnecessary attention and problems, thus training the skill only when nobody was around to see it. Even after nearly completing it, he did not use the skill against monsters unless in very dire situations.[8]

Dual Blades does not exist in ALfheim Online. Even if a player imports the skill from Sword Art Online, they will find that the skill cannot be identified by the system.[9]

Players may dual wield two swords even without having the Dual Blades skill.

In Sword Art Online, attacking without using Sword Skills is inefficient, as a regular attack with a sword is much weaker than an attack using a Sword Skill.[10]

In ALfheim Online, as there is no system assist for dual wielding, players need a lot of practice and experience for such a style to be efficient.[11]

Kirito using Skill Connect, with two swords.

In New ALfheim Online, with the introduction of Sword Skills, it is possible to chain in multiple one-handed sword Sword Skills by performing an activation motion with one sword during the post-motion delay phase of the other sword, thus cancelling out the delay. This strategy can only be used for skills where the last hit of a skill leaves the player in a position similar to that of another skill's activation motion.[12] This strategy is known as the Outside System Skill «Skill Connect».[13]

Although the Dual Blades Sword Skills are not available in ALO, with the introduction of Original Sword Skills, Kirito has been trying to reproduce his old Dual Blade skills as Original Sword Skills. So far, he has reproduced three of his Sword Skills, but he is having a hard time reproducing Starburst Stream.[1]

Kirito said that if Konno Yuuki had played Sword Art Online, she would have received the Dual Blades skill instead of him, due to her reaction time being much faster than his.[14]

In the PSP and PS Vita game adaptations of Sword Art Online: Infinity Moment and Hollow Fragment, the Dual Blades skill has several Sword Skills that were never used/seen in the light novels, anime, or manga. Though The Eclipse and Starburst Stream were included in its skill tree, their slashing motions were completely different.

In Episode 04, a member of the Titan's Handguild that attacked Kirito was armed with two axes and was still able to use Sword Skills, even though it is impossible to use Sword Skills armed with two weapons without the Dual Blades skill and Kirito was the only player to have this skill.

In Project Alicization, Kirito was able to use Sword Skills made for the Dual Blades skill in the final battle against Quinella, as Sword Skills in Project Alicization are not tied to Weapon Skills.